Avalanche Forecast
Issued: Mar 19th, 2018 11:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet.
NWAC,
Northwest Avalanche Center
Cool and spring-like conditions Tuesday will maintain stable snow in the morning hours. Sunshine and daytime warming will help soften the surface snow making shallow Loose-Wet avalanches possible on some steep sun exposed slopes. Watch for new roller balls or wet surface snow deeper than your ankle, and avoid travel on those steep slopes.
Summary
Detailed Forecast
Generally safe avalanche conditions exist. Shallow recent snow overlies a strong melt-freeze crust in most areas and should have a strengthening crust on the surface on aspects receiving sunshine. Freezing levels will continue to gradually rise on Tuesday relative to Monday, so the Loose Wet avalanche concern will remain one more day.
Strong sunshine and warmer temperatures will allow for gradually weakening and melting of the surface crust and underlying drier snow on steep sun-exposed slopes. Watch for signs of unstable snow, particularly in the Timberline area where greater fresh snow has fallen since Saturday. If you encounter roller-balling or natural Loose Wet avalanches, avoid travel on those steep sun exposed slopes.
Shallow wind slabs formed Saturday are expected to have stabilized and have been removed from the problems list. However, watch for any signs of recent wind-loading, mainly on N-SE facing slopes, steep convex roll overs, unsupported slopes, or on cross-loaded features above treeline.
Snowpack Discussion
Plentiful sunshine Monday is likely to have impacted or moistened recent snow on E-S-W aspects while warming temperatures should have moistened snow at lower elevations on all aspects.
Friday night and Saturday brought 9 inches of snow in the Timberline area, with only a few inches of new snow in the Mt Hood Meadows area. The new snow fell with cool temperatures and some moderate westerly winds near ridge crest Friday night. The most recent snow sits atop a melt-freeze crust.
Several melt-freeze cycles last weekend helped to consolidate and strengthen the snowpack. No recent avalanche activity has been reported at Mt. Hood.
While we are tracking several layers deeper in the snowpack, there are currently no significant layers of concern.
Observations
On Sunday, MHM pro patrol reported no reactivity to any older shallow wind slabs with only very shallow surface snow becoming moist.
On Friday, Pro-observer Laura Green found 2-4" of new snow near Timberline well bonded to the underlying crust. Poor visibility limited observations above treeline.
Problems
Loose Wet
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 20th, 2018 11:00AM
